Burst error rate, BER, is cumulative ratio of burst errors (uncorrectable FEC errors + No Unique Word errors) to total number of received bursts in percentage format.
BER Includes:
- Uncorrectable FEC
Uncorrectable FEC (forward error correction) is a condition where valid burst was received and demodulated; however, there were more errors in the burst than could be corrected by the FEC.
High number of uncorrectable FEC caused by:
o low SNR (link is too long),
o multipath fading
o Interference
- No Unique Word
No Unique Word Count indicates that some energy was detected (above the minimum power threshold) during a scheduled time slot, however no Unique Word was detected.
The Unique Word is an identifier that is part of the preamble of every wireless burst and must be valid in order for a burst to be properly demodulated.
No UW on the BSU caused by interference or collisions during contention requests, and it will degrade the sector performance.
No UW on the SU caused by Interference or radio too close to base (signal should be less than –45dBm), resulting in overdriving of the SU radio.
- No Energy errors
No energy error is when scheduled packet did not arrive, or arrived with very low power level (below the minimum energy level threshold).
On the BSU: error count increases for each frame that does not have contention traffic. This is a normal condition.
On the SU: Numerous NO ENERGY errors usually indicate a VERY low signal level. SU should be pointed again
BSU in a good condition have an errors < 1-2%. BSU with errors < 5 % is still accepted.
Higher number may caused by problems such as interference and can degrade performance.
What should we do if we found that BER counter more than 5%?
- Reset the BSU radio status counter.
- Step up the Rx power of the BSU (up to -60 dBm).
- Scan the frequency using the FSA tools that belong to the BSU.
- Switch the frequency.
- Replace the pigtail cable
- Decrease channel width
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